Cellular Respiration Cellular Respiration Cellular Respiration takes place

Cellular Respiration

Cellular Respiration: • Cellular Respiration takes place in both plant and animal cells. • It really takes place in nearly all cells. • Sometimes people think photosynthesis only takes place in plant cells and respiration only takes place in animal cells and this is not correct.

Cellular Respiration: • Cellular respiration is the process that takes the chemical energy from "food" molecules and releases it so that it can be captured (in part) in the form of ATP through phosphorylation. Cells can use carbohydrates, fats, and proteins as fuels for cellular respiration, however, glucose is most commonly used.

Cellular Respiration: • Cellular respiration occurs in both the cytoplasm and mitochondria.

2 Types of Cellular Respiration: ¶ Aerobic Respiration: with oxygen, i. Two Stages of aerobic respiration: Glycolysis: the splitting of glucose into 2 molecules of pyruvic acid (3 -carbon molecule – also called pyruvate) and the net release of 2 ATP (converts ADP and P into ATP - this is called substrate level phosphorylation) and 2 NADH molecules. • Takes place in the cytoplasm and has no oxygen requirement. • Occurs in nearly all organisms and probably evolved from ancient prokaryotes before oxygen was available.

Glycolysis in Detail Glycolysis generates ATP by substrate-level phosphorylation. Enzyme ADP Substrate Figure 9. 7 P + Product ATP

Glycolysis:

Glycolysis to the Citric Acid (Krebs) Cycle Before the citric acid cycle can begin Pyruvate must first be converted to acetyl Co. A, which links the cycle to glycolysis CYTOSOL MITOCHONDRION NAD+ NADH + H+ O– S Co. A C O 2 C C O O 1 3 CH 3 Pyruvate Transport protein Figure 9. 10 CH 3 Acetyle Co. A CO 2 Coenzyme A

2 Types of Cellular Respiration: ¶Aerobic Respiration: with oxygen, i. Two Stages of aerobic respiration: Break down (oxidizing) the pyruvic acid molecules using the Krebs Cycle and Electron Transport Chain to get CO 2, H 2 O and 36 ATP molecules.

The Krebs Cycle: • Takes place in the matrix of the mitochondria.

The Krebs Cycle: A. Citric Acid Production: • As pyruvic acid enters the mitochondrial matrix, a carbon is removed, forming CO 2, and electrons are removed, changing NAD+ to NADH. • Coenzyme A joins the 2 -carbon molecule, forming acetyl-Co. A. Acetyl-Co. A then adds the 2 -carbon acetyl group to a 4 carbon compound, forming citric acid.

Tribute to Hans Adolf Krebs

The Krebs Cycle: B. Energy Extraction: Citric acid is broken down into a 5 -carbon compound, then into a 4 -carbon compound. Along the way, two more molecules of CO 2 are released, and electrons join NAD+ and FAD, forming NADH and FADH 2. In addition, one molecule of ATP is generated. The energy tally from one molecule of pyruvic acid is 4 NADH, 1 FADH 2, and 1 molecule of ATP (2 x - since two pyruvic acid molecules enter the Krebs Cycle).

The Krebs Cycle (in more detail):

The Krebs Cycle (in more detail):

Electron Transport System: • • • Takes place in the inner mitochondrial membrane. The electron transport chain (ETC) consists of a series of molecules, mostly proteins, embedded in the inner mitochondrial membrane. Electrons lose energy as they pass from one coenzyme to the next. The final electron acceptor is oxygen. This is why it is aerobic. This energy is converted into ATP by chemiosmosis (hydrogen ions pass through the membrane through the protein ATP synthase, which converts ADP and P into ATP). This is called oxidative phosphorylation. This produces 90% of ATP produced by Aerobic Cellular Respiration.

Electron Transport System: • The electron transport chain allows the release of the large amount of chemical energy stored in reduced NAD+ (NADH) and reduced FAD (FADH 2). The energy released is captured in the form of ATP (3 ATP per NADH and 2 ATP per FADH 2). NADH + H+ + 3 ADP + 3 Pi + 1/2 O 2 → NAD+ + H 2 O + 3 ATP FADH 2 + 2 ADP + 2 Pi + 1/2 O 2 → FAD+ + H 2 O + 2 ATP

Electron Transport System:

Summary of ATP molecules produced by Aerobic Cellular Respiration: 1. Glycolysis: Glucose = 2 pyruvic acids + 2 NADH + 2 ATP 2. Krebs Cycle: 2 pyruvic acids = 8 NADH and 2 FADH 2 + 2 ATP 3. Electron Transport Chain: 10 NADH = 30 ATP 2 FADH 2 = 4 ATP Total of 36 ATP molecules (potentially).

Aerobic Respiration Equation: C 6 H 12 O 6 + 6 O 2 + 6 H 2 O 36 ATP (Energy) + 6 CO 2 + 12 H 2 O

A Simple Diagram of Cellular Respiration:

ATP Yield During Aerobic Cellular Respiration:

ATP Yield During Aerobic Cellular Respiration:

2 Types of Cellular Respiration: ·Anaerobic Respiration: without oxygen. Takes place in the cytoplasm when oxygen is not present in the cell. There are two types of anaerobic respiration:

2 Types of Cellular Respiration: ¬Alcohol Fermentation: The glucose molecules are converted to ethyl alcohol and 4 ATP molecules. Glucose (Glycolysis) 2 Pyruvates 2 Acetaldehydes + 2 CO 2 2 Ethanols

2 Types of Cellular Respiration: Lactic Acid Fermentation: The glucose molecules are converted to lactic acid and 4 ATP molecules. This leads to muscle fatigue, soreness and cramps. Glucose (Glycolysis) 2 Pyruvates 2 Lactates (lactate is eventually transported by blood to the liver and converted back to pyruvate)

A Detailed Diagram of Anaerobic Cellular Respiration:

Comparison of the different Types of Cellular Respiration: Aerobic Cellular Respiration Lactic Acid Fermentation Ethyl Alcohol Fermentation Glucose Glycolysis (pyruvic acid) CO 2 and H 2 O + 36 ATP Glucose Glycolysis (pyruvic acid) Lactic Acid + 2 ATP Glucose Glycolysis (pyruvic acid) Alcohol and CO 2 + 2 ATP

2 Types of Cellular Respiration: • Obviously aerobic respiration is much more effective than anaerobic respiration.

Energy and Exercise: • Muscle cells normally contain small amounts of ATP for a few seconds of intense activity. • Quick Energy: Once this ATP is gone, muscle cells produce most of their ATP by lactic acid fermentation (anaerobic). But this can only last for about 90 seconds. Afterwards, this lactic acid can be removed with extra oxygen (why you breathe hard after short intense exercise).

Energy and Exercise: • Long-Term Energy: for exercise longer than 90 seconds, your body must use aerobic cellular respiration to generate a continuous supply of ATP molecules. Your body stores energy in muscles and other tissues in the form of the carbohydrate glycogen. After 15 to 20 minutes of exercise you begin to run out of glycogen and your body begins to break down fats and eventually protein for energy.

Cellular Respiration: • Remember that cellular respiration is the process that takes the chemical energy from "food" molecules to form ATPs. • Cells can use carbohydrates, fats, and proteins as fuels for cellular respiration, however, glucose is most commonly used.

Energy in Cells:

Energy in Cells: